Attributional bias between groups has been shown to exist when group-boundaries are composed of attitudes that are self-defining (Kenworthy & Miller, 2002). We wanted to see if attributional bias between groups would exist when the attitude issue separating the groups was not self-defining. Further, we wanted to see whether a decision of the issue would affect attributional bias. This was done in an experiment where participants, high-school students, read about a hypothetical situation where a decision was to be made. The decision would affect the school’s students, but was not considered self-defining. The participants stated their preferred outcome of the decision. Outcome was manipulated to be either concordant or discordant with participants´ preferences. Further, decision-making form varied so that in one condition, participants were informed that in-group authorities (student representatives) had made the final decision, and in the other condition, the decision was made by out-group authorities (the principal and teachers). Results showed that attributional bias was present when attitude issue was not self-defining. When outcome supported preferred alternative, attributional bias was stronger. Being part of the winning side, that is the high-status group, provides self-validation and increases self-esteem (Tyler, 1994 ). This interpretation is supported by further analysis showing that high self-esteem was related to more attributional bias. Attributional bias was stronger when the decision was made by in-group authorities as compared to out-group authorities. When in-group members make a decision, attributional bias may increase as a function of in-group identification, which provides information about self-worth (Smith & Tyler, 1997).